You can do it without changing the meaning, as long as the particle "le" refers to the direct complement (accusative) noun. If the particle "le" refers to the indirect complement (dative) noun, then the meaning will change. Le llamo= I call him/her/you (formal) Lo llamo = I call him/you (masculine formal). La veo = I see her/you (feminine formal). That is because "llamar" (to call) is a verb that requires an accusative (direct complement). But if you use a verb that requires a dative (indirect complement) then the meaning will change. Tengo que decirle = I have to tell him/her/you (masculine and feminine formal). This is because if you use "le", the particle will refer to the dative noun, in this case, the person whom you have to tell whatever you have to tell him/her. But if you use "lo" or "la", these particles will refer to what is being said instead of whom will be told. Compare the previous sentence with the following ones. Tengo que decirlo ("lo" here could be referring to a secret, "el secreto" which is masculine)= I have to say it. Tengo que decirla ("la" here could refer to the answer, "la respuesta" which is feminine) = I have to say it. The meaning is the same if the particles "le", "la" and "lo" are placed before the verb. Le tengo que decir. Lo tengo que decir. La tengo que decir. I hope this helps.

http://www.rae.es/consultas/uso-de-los-pronombres-los-las-les-leismo-laismo-loismo I will add that many people in Spain and probably in South America use le/lo/la incorrectly. For example in Madrid people are "leista", which means that use "le" where they should use "lo/la". For example: ¿Has visto a Juan? Sí, lo vi ayer (correct). Many peole in Madrid say incorrectly "le vi ayer" (incorrect).

Hola! Por el ejemplo que das, tu pregunta esta orienta a lo que llamamos en gramatica 'complemento idirecto'. Existe una regla para saber con mucha facilidad cuando es LO y cuando es LA, y esta es, que los complementos siempre coinciden en genero y numero con lo que estan remplazando. Es decir, si llamamos a una mujer, decimos que LA llamamos, si llamamos a un hombre, decimos que LO llamamos'. Si llamamos a Clara, Lucia y Julieta, entonces LAS llamamos, y si llamamos a Juan, Sergio y Diego, entonces LOS llamamos. Sobre 'le' o 'les', es tambien correcto, mas formal, y se usa cuando tratamos a la persona de 'usted' (por lo cual el genero queda como algo neutro). ENG.: Hi there! According to your example, your question is realted to what is called in grammar CI (complemento indirecto), and there's a basic rule to know whether its right to say la or lo, and it is, that this CI's, always match in number and in gender with what they are replacing. Eg, if we called one guy, we say 'LO llame', and if we called a woman, we would say LA llame. Also, if we called many women, we say 'LAS llame', and if we called many guys we say 'LOS llame'. About 'LE', thats right too, but its not that popular, we use it when we wanna be formal, and it is neutral (nor masculin or feminin).

Lo (masculino) La (femenino) es lo correcto para los pronombres en función Objeto Directo. El problema es que en muchos casos lo hacemos mal y el LO muy frecuentemente lo sustituimos por LE. Por ejemplo para decir que quieres a una mujer dices LA quiero, no hay problemas ahí, Pero si lo dices de un hombre, nos resistimos a decir lo correcto LO quiero y tendemos a decir LE quiero. Pero este LEÍSMO (o sustitución errónea del "le"por el "lo") se da más en España que en Latinoamérica.

gracias :)